Reservoir Prediction in Offshore Clinoform Sequences, Guinea-Bissau

Sequence stratigraphy and clinoform decompaction in the offshore areas of Guinea Bissau has resulted in the identification of an Aptian aged carbonate platform that shows evidence for western progradation in response to relative sea level rise. Evidence also suggests an initial period of emergence prior to progradation. Decompacted clinoform slope angles upto 5° and seismic velocities support a carbonate composition with the Shu’aiba Formation of Oman considered as a possible analogue. Reservoir potential exists associated with platform margin and interior facies as well as possible karstification associated with the period of emergence.

Analysis of Albian aged clinoforms identified decompacted slope gradients ranging between 1.5° to 2.5°, values that typically coincide with sand dominated modern day sub-marine slopes. Comparison with worldwide examples suggests that the offshore clinoforms observed at Cabo to Gata, SE Spain are a potential analogue, with these clinoforms representing sandwaves/ridges formed through the action of shore parallel sub-littoral currents. A similar depositional process can be inferred in the Albian case as a means of explaining the over 100km north-south extension of the clinoforms. Sequence stratigraphic analysis indicates an overall transgressive period with the development of shelfal mudstones above the Albian clinoform interval during highest relative sea levels.